Ceiling lighting is, of course, widely used, especially in building space dedicated to commercial or institutional use, such as offices, stores, restaurants and schools, to name a few examples. By far the most common type of ceiling lighting in offices, stores and schools is provided by ceiling fluorescent tubes, which are well suited to providing a diffuse and high level of illumination. Incandescent lamps are used by restaurants, where softer, warmer and lower intensity lighting is desired. Nearly all ceiling lighting fixtures, both fluorescent and incandescent, include some sort of diffuser. Notwithstanding the implication of the term "diffuser," i.e., that a diffuser is used to spread the light from the tube or bulb or the lamp or lamps of the fixture throughout the room, the main function of the diffuser is to hide the tubes or bulbs so people in the room cannot see the intense light of the lamps themselves, especially in the case of incandescent lamps. The most common diffusers are translucent glass or plastic plates, boxes or gloves or some form of grille suitably fastened to the lamp holder. To a greater or lesser extent, such diffusers have a decorative function, but the opportunity for enhancement of the decorative characteristic of diffusers of presently known forms is somewhat limited by the nature of the materials (glass, plastic and, in the case of grilles, metal).